EP3916066A1 - Pre-crosslinked epoxy adhesives and adhesive tapes containing the same - Google Patents

Abstract

The invention relates to a process for producing a pre-crosslinked epoxy PSA and the epoxy PSAs obtained therefrom. The invention further relates to an adhesive tape which contains the epoxy PSA, and to its use for fixing point fixings or objects in automobiles. The invention also relates to a curable composition.

Description

The invention relates to a process for producing a pre-crosslinked epoxy PSA and the epoxy PSAs obtained therefrom. The invention further relates to an adhesive tape which contains the epoxy PSA, and to its use for fixing point fixings or objects in automobiles. The invention also relates to a curable composition.

State of the art

Epoxy-amine-based adhesives are known in the prior art. For example, describes the EP 2 553 035 A1 pre-networked systems. The core of the application is the combination of pre-crosslinking and a Tg above room temperature. In this way, tensions in the claimed "shape-memory" adhesive films cannot be relieved, since the tapes are below their glass transition temperature. Accordingly, such systems are not pressure-sensitive.

the US 20130267136 A1 discloses a method in which an epoxy resin mixture is mixed with a first hardener, which does not react with the epoxy resin at room temperature and a second hardener which has reacted. Accordingly, precured epoxy tapes are disclosed. However, these are not storage-stable at room temperature (storage at -30 ° C, described in paragraph [0084]).

task

The object of the invention is therefore to provide an adhesive tape with a pre-crosslinked epoxy PSA which has good storage stability at room temperature (23 ° C.), in particular over 2 months. Furthermore, the adhesive tapes should preferably be suitable for holding the substrates in position during a vertical crosslinking step.

solution

The object of the present invention was achieved by the specific epoxy pressure-sensitive adhesive, in particular by the use of specific polyetheramines as one of the hardeners and, moreover, that the epoxy conversion is in a certain ratio to the theoretical gel point, as well as the presence of a certain mixture Tg for the Epoxy resin and polyetheramine.

1. a) mindestens ein Polyetheramin, welches mindestens zwei endständige -NH₂ Gruppen, bevorzugt zwei oder drei endständige -NH₂ Gruppen, enthält und in alpha-Stellung zu mindestens einer -NH₂ Gruppe, bevorzugt allen -NH₂ Gruppen, mindestens einen Alkylrest, bevorzugt einen Methyl-, Ethyl-, oder -Propylrest, enthält;
2. b) mindestens ein Epoxidharz;
3. c) mindestens einen, von a) verschiedenen Härter;
4. d) gegebenenfalls mindestens einen Beschleuniger;
5. e) gegebenenfalls mindestens ein Additiv; wobei

der Epoxidumsatz U_epoxy = 0,85 α_gel bis 1,3 α_gel beträgt und α_gel der Gelpunkt der Zusammensetzung ist; und
der Mischungs-Tg der Komponenten a) und b) unter 0 °C liegt.In a first aspect, the invention therefore relates to a method for producing a pre-crosslinked PSA by bringing the following components into contact and then mixing:

1. a) at least one polyetheramine which contains at least two terminal -NH ₂ groups, preferably two or three terminal -NH ₂ groups, and in alpha position to at least one -NH ₂ group, preferably all -NH ₂ groups, at least one alkyl radical, preferably contains a methyl, ethyl or propyl radical;
2. b) at least one epoxy resin;
3. c) at least one hardener different from a);
4. d) if applicable, at least one accelerator;
5. e) optionally at least one additive; whereby

_{the epoxy} conversion U epoxy = 0.85 α _gel to 1.3 α _gel and α _{gel is} the gel point of the composition; and
the mixture Tg of components a) and b) is below 0 ° C.

In a second aspect, the invention relates to a pre-crosslinked pressure-sensitive adhesive, obtainable by a process of the present invention.

In a third aspect, the invention relates to an adhesive tape comprising the pre-crosslinked PSA according to the present invention.

In a fourth aspect, the invention relates to the use of the adhesive tape of the present invention for fixing point holders.

In a fifth aspect, the invention relates to the use of the adhesive tape of the present invention for fixing objects in automobiles.

1. a) mindestens ein Polyetheramin, welches mindestens zwei endständige -NH₂ Gruppen enthält und in alpha-Stellung zu mindestens einer-NH₂ Gruppe mindestens einen Alkylrest enthält;
2. b) mindestens ein Epoxidharz;
3. c) mindestens einen, von a) verschiedenen Härter;
4. d) gegebenenfalls mindestens einen Beschleuniger;
5. e) gegebenenfalls mindestens ein Additiv, wobei

der Mischungs-Tg der Komponenten a) und b) unter 0 °C liegt.In a sixth aspect, the invention relates to a curable composition comprising

1. a) at least one polyether containing at least two terminal -NH ₂ groups and at least one-NH ₂ group contains at least one alkyl group in the alpha position;
2. b) at least one epoxy resin;
3. c) at least one hardener different from a);
4. d) if applicable, at least one accelerator;
5. e) optionally at least one additive, wherein

the mixture Tg of components a) and b) is below 0 ° C.

"At least one" as used herein refers to 1 or more, for example 2, 3, 4, 5, 6, 7, 8, 9 or more. In connection with constituents of the compound described herein, this indication does not refer to the absolute amount of molecules but to the type of constituent. "At least one hardener" therefore means, for example, one or more different types of hardener and does not refer to the number of a single type of hardener in the composition.

Numerical values that are given herein without decimal places refer to the full stated value with one decimal place. For example, "99%" stands for "99.0%".

The expression “approximately” or “approximately” in connection with a numerical value relates to a variance of ± 10% based on the specified numerical value, preferably ± 5%, particularly preferably ± 1%.

The expression "essentially free of" according to the present invention is to be understood as meaning that the respective compound is present in such small amounts that it has no negative influence on the composition, in particular the respective compound is present in less than 0.5 wt %, preferably 0.1% by weight, even more preferably 0.01% by weight based on the total weight of the composition in the composition. In particular, the respective compound is not included in the composition at all.

According to the invention, the viscosity is determined as the dynamic viscosity as follows. The dynamic viscosity can be determined according to DIN 53019-1-2008-09. The viscosity is measured in a cylinder rotation viscometer with a standard geometry according to DIN 53019-1-2008-09 at a measuring temperature of 23 ° C. and a shear rate of 1 × s ^-1 .

According to the invention, the softening temperature is carried out according to the relevant method, which is known as ring and ball and is standardized according to ASTM E28-18. An HRB 754 ring-ball machine from Herzog is used to determine the adhesive resin softening temperature of the resins. Resin samples are first finely ground in a mortar. The resulting powder is in A brass cylinder with a bottom opening (inner diameter at the upper part of the cylinder 20 mm, diameter of the bottom opening of the cylinder 16 mm, height of the cylinder 6 mm) was filled and melted on a hot table. The filling quantity is chosen so that the resin completely fills the cylinder after melting without protruding. The resulting test specimen, including the cylinder, is placed in the test holder of the HRB 754. Glycerine is used to fill the temperature control bath, provided the adhesive resin softening temperature is between 50 ° C and 150 ° C. A water bath can also be used at lower adhesive resin softening temperatures. The test balls have a diameter of 9.5 mm and weigh 3.5 g. According to the HRB 754 procedure, the ball is placed above the test specimen in the temperature bath and placed on the test specimen. There is a collecting plate 25 mm below the bottom of the cylinder, and a light barrier 2 mm above it. During the measurement process, the temperature is increased at 5 ° C / min. In the temperature range of the adhesive resin softening temperature, the ball begins to move through the bottom opening of the cylinder until it finally comes to a standstill on the collecting plate. In this position it is detected by the light barrier and the temperature of the bath is registered at this point in time. There is a double determination. The adhesive resin softening temperature is the mean value from the two individual measurements.

The static glass transition temperature Tg is determined using dynamic differential calorimetry in accordance with DIN 53765: 1994-03. For this purpose, approximately 7 mg of the sample are weighed exactly into an aluminum pan and then introduced into the measuring device (device: DSC 204 F1, Netzsch). An empty crucible is used as a reference. Two heating curves are then recorded with a heating rate of 10 K / min. The information on the glass transition temperature Tg relates to the glass transition temperature Tg according to DIN 53765: 1994-03 of the second heating curve, unless otherwise stated in the individual case.

Information on the number-average molar mass Mn or the weight-average molar mass Mw are determined by measurement by means of gel permeation chromatography (GPC). It was measured against polystyrene standards.

The epoxy equivalent weight (EEW) of the respective component is preferably determined in accordance with DIN EN ISO 3001: 1999-11.

The amine equivalent weight (AHEW) is calculated from the molecular weight M _n and the number of amine hydrogens (-NH or -NH ₂ ) H _{eq of} the respective compound as follows:
AHEW = M _n / H _eq . For example, if the molecular weight of an amine is 1000 g / mol and the molecule has 2-NH ₂ groups (H _eq = 4 equivalents), the result is an AHEW = 250 g / eq.

Further reference methods emerge from the following description, in particular the test methods in the experimental part.

The preferred embodiments described below for the individual components a) to e) can be applied to all six aspects of the present invention.

These and other aspects, embodiments, features and advantages of the invention will become apparent to those skilled in the art from a study of the following detailed description and claims. Each feature from one aspect of the invention can be used in any other aspect of the invention. Furthermore, it goes without saying that the examples contained herein are intended to describe and illustrate the invention, but not to limit it, and in particular the invention is not limited to these examples.

1. a) mindestens ein Polyetheramin, welches mindestens zwei endständige -NH₂ Gruppen, bevorzugt zwei oder drei endständige -NH₂ Gruppen, enthält und in alpha-Stellung zu mindestens einer -NH₂ Gruppe, bevorzugt allen -NH₂ Gruppen, mindestens einen Alkylrest, bevorzugt einen Methyl-, Ethyl-, oder -Propylrest, enthält;
2. b) mindestens ein Epoxidharz;
3. c) mindestens einen, von a) verschiedenen Härter, insbesondere latenten Härter;
4. d) gegebenenfalls mindestens einen Beschleuniger, insbesondere latenten Beschleuniger; und
5. e) gegebenenfalls mindestens ein Additiv; wobei

der Epoxidumsatz U_epoxy = 0,85 α_gel bis 1,3 α_gel beträgt und α_gel der Gelpunkt der Zusammensetzung ist; und
der Mischungs-Tg der Komponenten a) und b) unter 0 °C liegt.The invention relates in particular to a method for producing a pre-crosslinked pressure-sensitive adhesive by bringing the following components into contact and then mixing:

1. a) at least one polyetheramine which contains at least two terminal -NH ₂ groups, preferably two or three terminal -NH ₂ groups, and in alpha position to at least one -NH ₂ group, preferably all -NH ₂ groups, at least one alkyl radical, preferably contains a methyl, ethyl or propyl radical;
2. b) at least one epoxy resin;
3. c) at least one hardener different from a), in particular latent hardener;
4. d) optionally at least one accelerator, in particular latent accelerator; and
5. e) optionally at least one additive; whereby

_{the epoxy} conversion U epoxy = 0.85 α _gel to 1.3 α _gel and α _{gel is} the gel point of the composition; and
the mixture Tg of components a) and b) is below 0 ° C.

The at least one polyetheramine preferably has a weight-average molecular weight of 150 to 6000 g / mol, preferably 200 to 3000 g / mol.

Suitable polyetheramines are, for example, from Huntsman Corp. commercially available under the tradename Jeffamine®. In particular, Jeffamine® of the D-series, T-series, ED series and XTJ series suitable. In order to keep the proportion of amines in the mixture as low as possible, polyetheramines with a low amine equivalent weight (AHEW) of less than 1000 g / eq are preferred. These are, for example, commercially available under the trade names Jeffamine® D-205, D-230, D-400, D-2000, D-2010, ED-600, ED-900, ED-2003, T-403, T-3000, THF -100 available. Trifunctional polyetheramines of the T-series, such as Jeffamine® T-403 and Jeffamine® T-3000, are particularly preferred, and Jeffamine® T-3000 is very particularly suitable.

In a preferred embodiment, the at least one polyetheramine a) is contained in 1 to 40% by weight, based on the total weight of a) and b). In a more preferred embodiment, the at least one polyetheramine is contained in 1 to 15% by weight, based on the total weight of a) and b), in particular if the at least one polyetheramine has an amine equivalent weight (AHEW) of less than 1000 g / eq. In an alternative, more preferred embodiment, the at least one polyetheramine is contained in 10 to 40% by weight, based on the total weight of a) and b), in particular if it is difunctional polyetheramines.

In general, all epoxy resins known to the person skilled in the art of pressure-sensitive adhesives are suitable as at least one epoxy resin. They can be aromatic or, in particular, aliphatic or cycloaliphatic in nature.

The one epoxy resin or the several epoxy resins can be the only reactive resins used, ie in particular the only components which with hardeners - if necessary after appropriate activation - can lead to curing of the composition. In principle, however, it is also possible that, in addition to the epoxy resin or in addition to the epoxy resins, further reactive resins that are not epoxy resins are present.

One or more elastomer-modified, in particular nitrile rubber-modified, epoxy resins and / or one or more silane-modified epoxy resins and / or one or more fatty acid-modified epoxy resins are used as epoxy resin b), for example and advantageously.

In the context of this document, epoxy resins are in particular those with more than one epoxy group per molecule, that is to say those reactive resins in which the functional groups or at least some of the functional groups are epoxy groups. The conversion of the epoxy resins during the hardening reaction of the hardenable composition takes place in particular via polyaddition reactions with suitable epoxy hardeners or via polymerization the epoxy groups. Depending on the choice of epoxy hardener, both reaction mechanisms can take place in parallel.

In one embodiment, the at least one epoxy resin has a Tg of -100 to 60.degree. C., preferably -50 to 40.degree.

In one embodiment, the at least one epoxy resin has an average functionality of 2 to 15, preferably 2 to 7.

In one embodiment, the at least one epoxy resin has a softening temperature of at least 45.degree. This is particularly the case in embodiments in which the proportion of low-viscosity polyetheramine in the mixture is greater.

In one embodiment, the at least one epoxy resin or at least one epoxy resin contained has a viscosity at 25 ° C. of at least 20 Pa * s, preferably 50 Pa * s, more preferably 150 Pa * s.

In one embodiment, at least one, preferably two, epoxy resin (s) that are liquid at 23 ° C. and at least one epoxy resin that is solid at 23 ° C. are contained.

Epoxy group-containing materials or epoxy resins useful in the compositions of the invention are any organic compounds having at least one oxirane ring which are polymerizable by a ring opening reaction. Such materials, commonly referred to as epoxides, include both monomeric and polymeric epoxides and can be aliphatic, cycloaliphatic, or aromatic. These materials preferably have on average at least two epoxy groups per molecule, preferably more than two epoxy groups per molecule. The "average" number of epoxy groups per molecule is defined as the number of epoxy groups in the epoxy-containing material divided by the total number of epoxy molecules present. The polymeric epoxides include linear polymers with terminal epoxy groups (e.g., a diglycidyl ether of a polyoxyalkylene glycol), polymers with backbone oxirane units (e.g., polybutadiene-polyepoxide), and polymers with pendant epoxy groups (e.g., a glycidyl methacrylate polymer or copolymer). The molecular weight of the epoxy-containing material can vary from 58 to about 100,000 g / mol or more. Mixtures of various epoxy-containing materials can also be used. Useful epoxy-containing materials include those containing cyclohexene oxide groups such as the epoxycyclohexane carboxylates represented by 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate and bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate are exemplified. For a more detailed list of useful epoxies of this type see on U.S. Patent No. 3,117,099 referenced.

Other epoxy-containing materials particularly useful in the practice of this invention include glycidyl ether monomers. Examples are the glycidyl ethers of polyhydric phenols obtained by reacting a polyhydric phenol with an excess of chlorohydrin such as epichlorohydrin (e.g. the diglycidyl ether of 2,2-bis- (2,3-epoxypropoxyphenol) propane). Further examples of epoxides of this type which can be used in the practice of this invention are shown in U.S. Pat U.S. Patent No. 3,018,262 described. In addition, epoxy-containing materials are included, which are obtained by modifying the abovementioned raw materials with fatty acids, in particular dimeric fatty acids.

There are a variety of commercially available epoxy-containing materials which can preferably be used in this invention. In particular, epoxides that are readily available include octadecylene oxide, epichlorohydrin, styrene oxide, vinyl cyclohexene oxide, glycidol, glycidyl methacrylate, diglycidyl ethers of bisphenol A (e.g. those sold under the trade names EPON 828, EPON 1004 and EPON 1001F from Shell Chemical Co. and DER-332 and DER-334 are available from Dow Chemical Co.), diglycidyl ether of bisphenol F (e.g. ARALDITE GY281 from Ciba-Geigy), vinylcyclohexene dioxide (e.g. ERL 4206 from Union Carbide Corp.), 3,4-ep-oxycyclohexylmethyl-3,4 epoxycyclohexenecarboxylate (e.g. ERL-4221 from Union Carbide Corp.), 2- (3,4-epoxy-xycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-metadioxane (e.g. ERL-4234 from Union Carbide Corp.) ), Bis (3,4-epoxycyclohexyl) adipate (e.g. ERL-4299 from Union Carbide Corp.), dipentene dioxide (e.g. ERL-4269 from Union Carbide Corp.), epoxidized polybutadiene (e.g. OXIRON 2001 from FMC Corp.), silicone resin-containing epoxy functionality , Epoxysilanes (e.g. beta- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and gamma-glycidoxypropyltrime thoxysilane, commercially available from Union Carbide), fire retardant epoxy resins (e.g. DER-542, a brominated bisphenol-type epoxy resin available from Dow Chemical Co.), 1,4-butanediol diglycidyl ether (e.g. B. ARALDITE RD-2 from Ciba-Geigy), hydrogenated epoxy resins based on bisphenol A-epichlorohydrin (e.g. EPONEX 1510 from Shell Chemical Co.) and polyglycidyl ethers of phenol-formaldehyde novolak (e.g. DEN-431 and DEN-438 from Dow Chemical Co.).

Particularly preferred epoxy resins are used - particularly advantageously in combination with one or more elastomer-modified and / or silane-modified and / or fatty acid-modified epoxy resins.

As elastomer-modified epoxides in the context of the present invention are - in particular liquid, usually highly viscous - epoxides with an average functionality of at least two and an elastomer content of up to 50 wt .-%, preferably with such a functionality of 5 to 40 wt .-% , to understand. The epoxy groups can be terminal and / or arranged in the side chain of the molecule. The elastomeric structural component of these flexibilized epoxies consists of polyenes, diene copolymers and polyurethanes, preferably of polybutadiene, butadiene-styrene or butadiene-acrylonitrile copolymers.

An epoxy resin modified by butadiene-acrylonitrile copolymers (nitrile rubber) is, for example, an epoxy prepolymer which is obtained by modifying an epoxy resin with at least two epoxy groups in the molecules with a nitrile rubber. A reaction product of glycerol or propylene glycol and a halogen-containing epoxy compound, such as epichlorohydrin, or the reaction product of a polyhydric phenol, such as hydroquinone, bisphenol-A, and a halogen-containing epoxide, is advantageously used as the epoxy base. A reaction product of a bisphenol A type epoxy resin having two terminal epoxy groups is desirable.

To bind the epoxy resins, in the case of butadiene polymers or butadiene-acrylonitrile copolymers (so-called nitrile rubbers), a third monomer with an acid function - for example acrylic acid - can also be polymerized, which gives so-called carboxy-terminated nitrile rubbers (CTBN). As a rule, these compounds contain acid groups not only at the ends, but also along the main chain. CTBN are offered, for example, under the trade name Hycar from B. F. Goodrich. These have molar masses between 2000 and 5000 g / mol and acrylonitrile contents between 10% and 30%. Specific examples are Hycar CTBN 1300 x 8, 1300 x 13 or 1300 x 15. The reaction with butadiene polymers proceeds accordingly.

By reacting epoxy resins with CTBN, so-called epoxy-terminated nitrile rubbers (ETBN) are obtained, which are used with particular preference for this invention. Such ETBNs are commercially available, for example, from Emerald Materials under the name HYPRO ETBN (previously Hycar ETBN) - such as Hypro 1300X40 ETBN, Hypro 1300X63 ETBN and Hypro 1300X68 ETBN. An example of an epoxy-terminated butadiene rubber is Hypro 2000X174 ETB.

Further examples of elastomer-modified epoxy-functional compounds are a reaction product of a diglycidyl ether of neopentyl alcohol and a butadiene / acrylonitrile elastomer with carboxyl ends (e.g. EPONTM Resin 58034 from Resolution Performance Products LLC), a reaction product of a diglycidyl ether of bisphenol A and a butadiene / acrylonitrile elastomer with carboxyl ends (e.g. EPONTM Resin 58006 from Resolution Performance Products LLC), a butadiene / acrylonitrile elastomer with carboxyl ends (e.g. CTBN-1300X8 and CTBN-1300X13 from Noveon, Inc., Cleveland, Ohio) and an amine-terminated butadiene / acrylonitrile elastomer (e.g., ATBN-1300X16 and ATBN-1300X42 from Noveon, Inc.). An example of the elastomer-modified epoxy resin adduct is the reaction product of an epoxy resin based on bisphenol F and a butadiene / acrylonitrile elastomer with carboxyl ends (e.g. EPON ™ Resin 58003 from Resolution Performance Products LLC).

The proportion of elastomer-modified epoxy resins based on the total amount of epoxy resins can be between 0 and 100% by weight. For bonds with particularly high bond strengths and low elongation, rather lower proportions - such as, for example, 0 to 15% by weight - are chosen. In contrast to this, adhesives with high elongation values are obtained when the proportion is greater than 40% by weight, in particular greater than 60% by weight. For many applications, a balanced relationship between bond strength and elongation is desired. Here proportions between 20 to 60% by weight, in particular 30 to 50% by weight, are preferred. Depending on the requirement profile, it can also be advantageous to use adhesives with a proportion of up to 100%.

In order to achieve sufficient crosslinking in the pre-crosslinking step, epoxy resins are preferably used which have a functionality of at least 2 (f 2). The addition of epoxy resins with higher functionality (f> 2) is helpful to achieve pre-crosslinking and to keep conversion as low as possible, which is important for good tack. These higher functional resins are often solids, such as epoxy novolaks.

Alternatively, liquid, higher-functionality epoxy resins can make up up to 100% by weight of the epoxy resin mixture.

In order to achieve good bonding properties of the cured adhesive, it preferably does not contain more than 70% by weight of liquid epoxy resins. A preferred amount of higher-functionality solid resins in the epoxy resin mixture is between 10% by weight and 70% by weight, in particular less than 50%. Are monofunctional epoxy resins such as Butyl glycidyl ether, cresyl glycidyl ether or other alkyl glycidyl ethers are used, their proportion of the total amount of epoxy resins is not greater than 15% by weight, preferably 10% by weight, in particular less than 5% by weight, based on the total weight of the epoxy resins contained.

In a preferred embodiment, the at least one epoxy resin b) is contained in 60 to 99% by weight, based on the total weight of a) and b). In a more preferred embodiment, the at least one epoxy resin is contained in 85 to 99% by weight, based on the total weight of a) and b), in particular if the at least one polyetheramine has an amine equivalent weight (AHEW) of less than 1000 g / eq. In an alternative, more preferred embodiment, the at least one epoxy resin is contained in 60 to 90% by weight, based on the total weight of a) and b), in particular if a) is difunctional polyetheramines.

It also contains at least one further hardener c) different from the polyetheramine. The polyetheramine acts as the first hardener (precrosslinker) during the first crosslinking. Suitable (latent) hardeners c) essentially do not react in the pre-crosslinking step, that is, in the first crosslinking.

Such hardeners c) are referred to in this document in accordance with DIN 55945: 1999-07 - the chemical compound (s) acting as binding agent (s) which is (are) added to the crosslinkable resins in order to achieve the final hardening ( Crosslinking) of the curable composition, in particular in the form of an applied film. The compositions of the present invention can also optionally contain at least one accelerator.

In the context of this document, (latent) accelerators d) are those chemical compounds which, in the presence of another hardener c), increase the reaction rate of the hardening reaction and / or the rate of activation of the hardening of the epoxy resins, in particular in the sense of a synergism.

In dynamic differential calorimetry (DSC), hardening reactions can basically be identified as exothermic peaks. The measuring method according to DIN 53765: 1994-03 is used. The temperature at the maximum of this exothermic peak at a heating rate of 10K / min used is referred to as T _peak .

Accelerators are to be understood in particular as those compounds, the addition of which shifts the hardening peak of a specific hardener to lower temperatures.

In contrast to the individual hardeners and accelerators, the term hardening reagent refers to the entirety of the hardeners used and, if necessary, accelerators for the hardening reaction by means of the corresponding reactive component (the corresponding reactive resin (s)). In the present invention, the hardening reagent can accordingly be formed in particular from one or more hardeners and the polyetheramine or from one or more hardeners and the polyetheramine in the presence of one or more accelerators.

Particularly advantageous compounds from the following list of dicyandiamide, anhydrides, epoxy-amine adducts, phenol novolaks, cresol novolaks, hydrazides and reaction products of diacids and multifunctional amines can be selected as hardeners c). Reaction products from diacids and multifunctional amines are, for example, reaction products from phthalic acid and diethylenetriamine. In a very preferred embodiment of the invention, the curing reagent comprises dicyandiamide and one or more imidazole compounds (e.g. selected from the Curezol series available from Evonik Industries AG).

In a preferred embodiment, the at least one hardener c) different from a) is selected from dicyandiamides, phenol novolaks, cresol novolaks, anhydrides, epoxy-amine adducts, hydrazides or mixtures thereof.

In one embodiment, the at least one hardener c) different from a) has a T _peak, determined by DSC as described above, of more than 60 ° C., preferably more than 80 ° C., in particular more than 100 ° C.

In a preferred embodiment, the proportion of the at least one further hardener c) different from a) is determined via the epoxy equivalent weight (EEW) of the epoxy mixture and the amine equivalent weight (AHEW). It has been shown here that, particularly when using dicyandiamide as hardener, at least 90% of the theoretically required amount of amine is preferred, but can also be used well above the equimolar amount, for example 130%, 150% or 200%.

wobei

• m_ges = Summe m_i
• m_i Massen der einzelnen Komponenten i der Mischung
• EEW_i = Epoxyäquivalente der Komponenten i

Stoichimetric hardeners such as dicyandiamide are preferably used based on the amount of epoxy in the adhesive. To do this, the EEW of the epoxy mixture is first calculated using the following formula: $${\mathrm{EEW}}_{\mathrm{total}}={{}^{{\mathrm{m}}_{\mathrm{total}}}/}_{\sum \frac{{\mathrm{m}}_{\mathrm{i}}}{{\mathrm{EEW}}_{\mathrm{i}}}}$$

whereby

• m _tot = sum m _i
• m _i masses of the individual components i of the mixture
• EEW _i = epoxy equivalents of components i

The amount of hardener _H m is then obtained from the amine equivalent of the curing agent (AHEW) and the EEW of the epoxy mixture _ges as follows: $${\mathrm{m}}_{\mathrm{H}}=\mathrm{AHEW}*\left({\mathrm{m}}_{\mathrm{i}}/{\mathrm{EEW}}_{\mathrm{total}}\right)$$

When calculating, the amount of polyetheramine a) used must be taken into account, as this already converts part of the epoxy groups, so that there is a reduced amount of hardener for c). This is shown in an example: For pre-crosslinking, an epoxy conversion of 15% is achieved and a corresponding amount of polyetheramine is used. The amount of hardener is reduced accordingly by 15%.

For epoxy-amine adducts, it is preferred that, based on the weight of the at least one epoxy resin b), between 10% by weight and 30% by weight of c) are used.

In one embodiment, the accelerator d) is selected from urea derivatives, which are sold, for example, under the trade name Dyhard UR from Alzchem, or imidazoles, such as those available under the trade name Curezol from Evonik Industries AG, or epoxy-amine adducts, such as those from Ajinomoto marketed under the trade name Ajicure. Particularly preferred urea derivatives are dimethyl urea derivatives such as Dyhard UR500 or Dyhard UR700. Preferred imidazoles that give adequate storage stability are, for example, in WO 2019101918 A1 and explicitly listed here as preferred compounds. Suitable epoxy-amine adducts are in the US 6,838,170 B2 under the heading "adducts" disclosed, as well as in the US 9,589,693 B2 under the term "amine-epoxy adducts".

In a preferred embodiment, the at least one accelerator is used, based on the weight of the at least one epoxy resin b) 0.25% by weight and 5% by weight.

Furthermore, at least one additive which is different from components a) to d) can optionally be contained. All additives known to the person skilled in the art of pressure-sensitive adhesives are suitable.

For example, the additives are selected from polymers, resins, dyes and solids for adjusting the electrical or thermal conductivity or mixtures thereof.

In one embodiment, the at least one additive is contained in 0.001 to 5% by weight, preferably 0.01 to 3% by weight, based on the total weight of components a) to c).

In general, all additives known to the person skilled in the art of PSAs are suitable. These can be selected, for example, from rheology modifiers, foaming agents, fillers or adhesion promoters.

• Plastifizierungsmittel wie zum Beispiel Weichmacheröle, oder niedermolekulare flüssige Polymere, wie zum Beispiel niedermolekulare Polybutene, vorzugsweise mit einem Anteil von 0,2 bis 5 Gew.-% bezogen auf das Gesamtgewicht der Haftklebemasse
• primäre Antioxidantien wie zum Beispiel sterisch gehinderte Phenole, vorzugsweise mit einem Anteil von 0,2 bis 1 Gew.-% bezogen auf das Gesamtgewicht der Haftklebemasse
• sekundäre Antioxidantien, wie zum Beispiel Phosphite oder Thioether, vorzugsweise mit einem Anteil von 0,2 bis 1 Gew.-% bezogen auf das Gesamtgewicht der Haftklebemasse
• Prozessstabilisatoren wie zum Beispiel C-Radikalfänger, vorzugsweise mit einem Anteil von 0,2 bis 1 Gew.-% bezogen auf das Gesamtgewicht der Haftklebemasse
• Lichtschutzmittel wie zum Beispiel UV-Absorber oder sterisch gehinderte Amine, vorzugsweise mit einem Anteil von 0,2 bis 1 Gew.-% bezogen auf das Gesamtgewicht der Haftklebemasse
• Verarbeitungshilfsmittel, vorzugsweise mit einem Anteil von 0,2 bis 1 Gew.-% bezogen auf das Gesamtgewicht der Haftklebemasse
• gegebenenfalls weitere Polymere von bevorzugt elastomerer Natur; vorzugsweise mit einem Anteil von 0,2 bis 10 Gew.-% bezogen auf das Gesamtgewicht der Haftklebemasse.

The following compounds are also suitable as further additives:

• Plasticizers, such as, for example, plasticizer oils, or low molecular weight liquid polymers, such as, for example, low molecular weight polybutenes, preferably in a proportion of 0.2 to 5% by weight, based on the total weight of the pressure-sensitive adhesive
• primary antioxidants such as, for example, sterically hindered phenols, preferably in a proportion of from 0.2 to 1% by weight, based on the total weight of the pressure-sensitive adhesive
• secondary antioxidants, such as, for example, phosphites or thioethers, preferably in a proportion of from 0.2 to 1% by weight, based on the total weight of the pressure-sensitive adhesive
• Process stabilizers such as, for example, C radical scavengers, preferably in a proportion of from 0.2 to 1% by weight, based on the total weight of the pressure-sensitive adhesive
• Light stabilizers, such as, for example, UV absorbers or sterically hindered amines, preferably in a proportion of from 0.2 to 1% by weight, based on the total weight of the pressure-sensitive adhesive
• Processing aids, preferably in a proportion of from 0.2 to 1% by weight, based on the total weight of the pressure-sensitive adhesive
• optionally further polymers, preferably of an elastomeric nature; preferably in a proportion of 0.2 to 10% by weight, based on the total weight of the pressure-sensitive adhesive.

If larger gaps are to be bridged, the pressure-sensitive adhesive can be in the form of a foam or it can take place in the curing step of the second hardener. The foaming can take place by means of any chemical and / or physical methods. However, a foamed PSA of the invention is preferably obtained by the introduction and subsequent expansion of microballoons.

In order to obtain the pre-crosslinked PSAs of the invention, there is a certain _epoxy conversion U epoxy. The epoxy conversion is U _epoxy = 0.85 α _gel to 1.3 α _gel , preferably U _epoxy = 0.9 α _gel to 1.3 α _gel , in particular U _epoxy = 0.95 α _gel to 1.3 α _gel .

• f_Amin = Funktionalität der Amine
• f_Epoxy = Funktionalität der Epoxidharze.

The gel point α _gel is calculated using the following equation: $${\alpha }_{\mathit{gel}}=\frac{1}{\left(f_{\mathit{Amine}}-1\right)\left(f_{\mathit{Epoxy}}-1\right)}$$

• f _amine = functionality of the amines
• f _Epoxy = functionality of the epoxy resins.

bzw. $$f_{\mathit{Aminmischung}}=\frac{\left(n_1\cdot f_1\right)+\left(n_2\cdot f_2\right)+\cdots }{n_1+n_2+\cdots }$$

wobei n_i die jeweilige Stoffmenge von Epoxid i bzw. Amin i und f_i die jeweilige Funktionalität von von Epoxid i bzw. Amin i bezeichnet.If mixtures of epoxy resins or amines are used, the functionality of a mixture is calculated using the following formula: $$f_{\mathit{Epoxy\; mix}}=\frac{\left(n_1\cdot f_1\right)+\left(n_2\cdot f_2\right)+\cdots }{n_1+n_2+\cdots }$$

respectively. $$f_{\mathit{Amine\; mixture}}=\frac{\left(n_1\cdot f_1\right)+\left(n_2\cdot f_2\right)+\cdots }{n_1+n_2+\cdots }$$

wherein n _{i represents} the respective molar amount of epoxy and amine i i and f _i of the respective functionality of epoxy amine i and i, respectively.

In these cases, the theoretical gel point is calculated using the following adapted equation from above: $${\alpha }_{\mathit{gel}}=\frac{1}{\left(f_{\mathit{Amine\; mixture}}-1\right)\left(f_{\mathit{Epoxy\; mix}}-1\right)}$$

wobei w₁, w₂, ... die jeweiligen Gewichtsteile der entsprechenden Bestandteile der Mischung und ihren jeweiligen Glasübergangstemperaturen T_g1, T_g2, ... entspricht.Furthermore, the mixture Tg of components a) and b) is below 0 ° C.
The mixture Tg is determined using the Fox equation: $$\frac{1}{T_G}=\frac{w_1}{T_{G1}}+\frac{w_2}{T_{G2}}...$$

where w ₁ , w ₂ , ... correspond to the respective parts by weight of the respective constituents of the mixture and their respective glass transition temperatures T _g1 , T _g2 , ...

The process can be carried out in a mixer. In one embodiment, the components are heated together before mixing, preferably to 40 to 100 ° C., in particular for 1 to 30 minutes. In one embodiment, the components are heated during mixing, preferably to 40 to 80 ° C., in particular for 1 to 30 minutes. In one embodiment, the addition of the at least one hardener c) and / or the at least one accelerator d) is carried out at temperatures of less than 80 ° C., preferably less than 60 ° C., at the end of the mixing process.

With the process of the present invention, pre-crosslinked PSAs are obtained.

The invention further relates to adhesive tapes which comprise the pre-crosslinked PSAs of the present invention.

In one embodiment, the PSA has a layer thickness of 20 to 4000 μm. In a preferred embodiment, the layer thickness is 20 to 150 μm. This makes the adhesive tapes suitable for the electronics sector. In an alternative preferred embodiment, the layer thickness is 200 to 2000 μm, in particular 400 to 1000 μm. This makes the adhesive tapes suitable for the automotive sector.

duct tape

The curable composition of the adhesive tape of the invention is the pre-crosslinked adhesive of the present invention. These are reactive adhesives which comprise chemically reactive systems which, when activated, lead to a hardening reaction and which can develop particularly high bond strengths (in particular greater than 1 MPa) to the substrates to which they are bonded.

With the attribute "pressure-sensitive" - also as a component of nouns such as in pressure-sensitive adhesive - or synonymous with the attribute "self-adhesive" - also as a component of nouns - In the context of this document, those compositions are referred to which allow a permanent bond with the primer under relatively light pressure - unless otherwise stated, at room temperature, i.e. 23 ° C - and can be removed from the primer after use essentially without leaving any residue. Pressure-sensitive adhesives are preferably used in the form of adhesive tapes. For the purposes of the present invention, a pressure-sensitive adhesive tape has a bond strength in the uncured (ie pre-crosslinked) state of at least 1 N / cm. The bond strength here is determined on steel analogously to ISO 29862: 2007 (method 3) at 23 ° C. and 50% relative humidity at a peel speed of 300 mm / min and a peel angle of 180 °. An etched PET film with a thickness of 36 μm, as is available from Coveme (Italy), is used as the reinforcement film. A measuring strip 2 cm wide is glued using a rolling machine weighing 4 kg at a temperature of 23 ° C. The tape is peeled off immediately after application. The measured value (in N / cm) was the mean value from three individual measurements.
Pressure-sensitive adhesives thus have a permanently tacky effect at room temperature, that is to say they have a sufficiently low viscosity and high tack so that they wet the surface of the respective adhesive base even when there is little pressure. The adhesiveness of the pressure-sensitive adhesives is based on their adhesive properties and the redetachability on their cohesive properties. Pressure-sensitive reactive adhesives have pressure-sensitive adhesive properties at room temperature (and are especially viscoelastic in this state), but exhibit the behavior of reactive adhesives during and after curing.

According to the invention, the pre-crosslinked PSA is used in film or layer form as a component of an adhesive tape.

For this purpose, the pre-crosslinked PSA is applied as a layer to a permanent or a temporary carrier, in particular using the coating processes known to the person skilled in the art. The coating of the web-like material is preferably carried out without solvents, for example by means of nozzle coating or with a multi-roller applicator. This can be done particularly effectively and advantageously with a 2- to 5-roller applicator, for example with a 4-roller applicator, so that the self-adhesive is formed to the desired thickness when passing through one or more roller gaps before transfer to the web-like material. The rollers of the applicator can be individually tempered, for example set to temperatures of 20 ° C to 150 ° C.

If the coating is carried out using solvents, then these are removed again after the coating step in a suitable drying channel, so that the final web-like material has essentially no solvents (in particular less than 1% by weight, preferably less than 0.1% by weight %) contain.

Permanent carriers are, in particular, permanent constituents of single- or double-sided adhesive tapes in which one or both of the outer surfaces of the adhesive tape is formed by a layer of pressure-sensitive adhesive. For better handling, the adhesive layers can be covered with anti-adhesive separating layers, such as siliconized papers, which are removed in each case for bonding.

The general term “adhesive tape” thus encompasses, on the one hand, a carrier material which is provided with a pressure-sensitive adhesive on one or both sides and can optionally have further layers in between.

In particular, the expression “adhesive tape” in the context of the present invention encompasses so-called “transfer adhesive tapes”, that is to say adhesive tapes without a permanent carrier, in particular single-layer adhesive tapes without a permanent carrier.

Such adhesive transfer tapes according to the invention are applied to a temporary carrier prior to application. In particular, flexible sheet-like materials (plastic films, papers or the like) which are provided with a separating layer (for example siliconized) and / or have anti-adhesive properties (so-called separating materials, liners or release liners) serve as temporary carriers.

Temporary carriers serve in particular to make single-layer or otherwise non-self-supporting adhesive tapes - that is, which in particular consist only of the pressure-sensitive adhesive layer - manageable and to protect.

The temporary carrier can be easily removed and is removed during use (usually after the free adhesive tape surface has been applied to the first substrate and before the other, initially covered, adhesive tape surface is bonded to the second substrate), so that the pressure-sensitive adhesive layer can be used as a double-sided adhesive tape can.

Before application, adhesive transfer tapes according to the invention can also have two temporary carriers, between which the adhesive is present as a layer. For application, a liner is then regularly first removed, the pressure-sensitive adhesive applied and then the second liner removed. The PSA can thus be used directly to join two surfaces. Such carrierless adhesive transfer tapes are particularly preferred according to the invention. With such a pressure-sensitively adhesive, backing-free adhesive transfer tape according to the invention, adhesive bonding that is very precise in terms of positioning and metering is made possible.

Adhesive tapes are also possible in which one does not work with two liners, but with a single liner equipped with double-sided separation. The upper side of the adhesive tape web is then covered with one side of a double-sided separating liner, its underside with the back of the double-sided separating liner, in particular an adjacent turn on a bale or roll.

In particular, adhesive tapes differ - regardless of whether they have a carrier or are without a carrier, i.e. adhesive transfer tapes - from layers of adhesive that are present on a substrate as a liquid adhesive, for example, in that the adhesive tapes are self-supporting, i.e. can be handled as an independent product. For this purpose, the pressure-sensitive adhesive layer has sufficient cohesion and / or the entirety of the layers forming the adhesive tape in particular has sufficient stability.

Adhesive tapes that are coated on one or both sides with adhesives are usually wound or cross-wound into a roll in the form of an Archimedean spiral at the end of the manufacturing process. In order to prevent the PSAs from coming into contact with one another in the case of double-sided adhesive tapes, or in order to prevent the PSA from sticking to the carrier in the case of single-sided adhesive tapes, the adhesive tapes, if not already present on a liner, can advantageously be or covered on both sides with a liner that is rolled up together with the adhesive tape. In addition to covering single or double-sided adhesive tapes, liners are also used to cover pure adhesive compounds (transfer tape) and sections of adhesive tape (e.g. labels). These liners also ensure that the pressure-sensitive adhesive is not soiled before use.

The final curing of the adhesives or adhesive tapes of the invention after application can advantageously take place at temperatures between 120 ° C. and 200 ° C. for 10 to 120 minutes. The exact conditions depend on the hardener c) and the hardener used optionally used accelerator d) and the amount of accelerator used. Typically, accelerators between 0.5 phr and 5 phr are used, phr referring to the amount of epoxy resins used. Exemplary curing conditions are 30 minutes at 180 ° C, 30 minutes at 160 ° C, 35 minutes at 145 ° C, 60 minutes at 130 ° C, 120 minutes at 120 ° C.

The adhesive tapes of the present invention are used for fixing point fixings and for fixing objects in automobiles, preferably for structural bonding of metal sheets.

Experimental part General manufacturing process

The raw materials of the corresponding example compositions from Table 1 without the accelerator were weighed into a beaker and heated to 80 ° C. for 5 minutes. The mixture was then homogenized in a Speedmixer DAC 600.2 from German Engineering by Hausschild for 5 minutes at 2500 rpm. The composition was allowed to cool to 60 ° C. The accelerator was then added and the mixture was homogenized again for 1 minute at 2500 rpm. After 60 minutes, the already slightly pre-reacted adhesive was poured onto a siliconized PET liner and pressed with 100 μm spacers between two steel plates at 25 kN to form a film. The films were stored for 7 days at 23 ° C, 50% r.h. stored to complete the 1st curing step.

Methods used Loss of adhesive strength (KK loss)

The bond strengths were determined analogously to ISO 29862: 2018-05 (method 3) at 23 ° C and 50% relative humidity with a peel speed of 300 mm / min and a peel angle of 180 °. The thickness of the adhesive layer was 100 μm in each case. An etched PET film with a thickness of 50 μm, such as is available from Coveme (Italy), was used as the reinforcement film.

Steel plates according to the standard were used as the substrate. The measuring strips were bonded using a rolling machine weighing 4 kg at a temperature of 23 ° C. The adhesive tapes were peeled off immediately after application. The KK loss is calculated from the KK value measured after storage of the adhesive film at 23 ° C / 50% RH for 2 months in relation to the fresh value after 7 days after production of the adhesive film (according to Completion of the 1st curing step). A KK loss of 100% indicates that the film has hardened to such an extent that it is no longer tacky.

Slipping

To assess the vertical holding force of the adhesives, a 19 g steel plate with a bond area of 2.5 × 2.5 cm was bonded to a glass plate. The position of the lower edge of the steel plate was marked on the glass plate. The adhesive was cured standing vertically at 180 ° C. for 30 minutes. After cooling, it was measured how many millimeters the steel plate had moved.

Bond strength (tensile shear test)

The bond strength of a cured composite produced by the method according to the invention for the different adhesive tapes was determined as a parameter for the quality of the bond achieved. The bond strength was determined quantitatively in a dynamic tensile shear test based on DIN-EN 1465-2009-07 at 23 ° C. and 50% RH for a test speed of 10 mm / min (results in N / mm ² = MPa). The test rods used were those made of steel, which were cleaned with acetone before bonding. The layer thicknesses of the adhesive tapes each corresponded to 100 μm ± 10 μm. The mean value from three measurements is given. Bondings with cured adhesives were measured. The curing took place at 180 ° C ± 2 ° C for 30 minutes.

Sales epoxy

The conversion of the epoxy-amine reaction was determined with ATR-FT-IR. The epoxy band at 914 cm ^{-1 was} used for this.

Networking test

A pre-crosslinked adhesive tape sample (1 × 1 cm, 100 μm layer thickness) was placed in a vial with butanone at 23 ° C. for 24 hours. An optical evaluation was carried out. If a sample was still visible in the vial after the solvent treatment, the sample was cross-linked. If the adhesive tape dissolves or breaks up into many small (partially cross-linked) particles, the test is considered not to be cross-linked.

Examples

Epiclon 673

Festes Epoxy-Kresol-Novolak der Firma DIC mit einer Erweichungstemperatur 75 bis 79 °C. Mittlere Funktionalität: 5,4 Epoxygruppen / Molekül, EEW= 208 - 212 g/eq. Tg = 30 °C

Epikote 828

Difunktionelles Bisphenol-A / Epichlorhydrin Flüssigepoxid mit einem Gewicht pro Epoxid von 184 bis 190 g/eq der Firma Hexion. Viskosität bei 25 °C von 10 bis 12 Pa s. Mittlere Funktionalität: 2 Epoxygruppen / Molekül. Tg = -16°C.

PolyDis PD3611

Nitrilkautschukmodifiziertes Epoxidharz auf der Basis von Bisphenol-F-diglycidylether mit einem Elastomergehalt von 40 Gew.-% und einem Gewicht pro Epoxid von 550 g/eq der Firma Schill + Seilacher "Struktol". Viskosität bei 25 °C von 10000 Pa s. Mittlere Funktionalität: 2 Epoxygruppen / Molekül. Tg = -10°C.

Hypro 1300X45 ATBN

Aminterminiertes Butadienacrylnitrilcopolymer mit 18% Acrylnitrilgehalt. Viskosität bei 27°C von 375 Pa s. Molekulargewicht 3800 g/mol. Tg =-55°C. Funktionalität = 1,8. Das zur Terminierung verwendete Amin ist N-Aminoethylpiperazin.

Jeffamine T403

Aminterminiertes Propylenoxid mit 3 primären Aminogruppen, die am Nachbarkohlenstoff eine Methylgruppe tragen. Tg = -61 °C. Molekulargewicht = 440 g/mol, mittlere Funktionalität: 5,7

Jeffamine T3000

Aminterminiertes Propylenoxid mit 3 primären Aminogruppen, die am Nachbarkohlenstoff eine Methylgruppe tragen. Tg = -70°C. Molekulargewicht = 3000 g/mol, mittlere Funktionalität: 5,91

Dyhard 100S

Latenter Härter der Firma AlzChem für Epoxidsysteme bestehend aus mikronisiertem Dicyandiamid bei dem 98 % der Partikel kleiner 10 µm sind.

Dyhard UR500

Latenter Uronbeschleuniger für Epoxidsysteme bei dem 98 % der Partikel kleiner 10 µm sind.

Tabelle 1: K= Erfindungsgemäße Klebemasse; V= Vergleichsbeispiel f Tg / °C K1 K2 K3 K4 V1 V2 V3 V4 Epiclon N-673 5,4 30 11,81 11,81 11,81 11,81 20,25 15,81 10,16 PD3611 2 -10 14,73 14,73 14,73 14,73 18 19,71 12,67 Epikote828 2 -16 11,81 11,81 11,81 11,81 6,75 30 15,81 10,16 Jeffamin T403 5,7 -61 1,45 1,23 Jeffamin T3000 5,91 -70 9,86 11,44 8,86 21,11 6,8 Hypro 1300X45 ATBN 1,8 -52 60 Dyhard 100S 2,34 2,29 2,38 2,36 2,46 2,87 2,07 Dyhard UR500 0,17 0,16 0,17 0,17 0,19 0,21 0,15 Mischungs-Tg (Epoxy-Amin-Mischung) / °C -18,6 -20,6 -17,2 -4,2 4,3 -25,5 -15,8 f(epoxy) 2,64 2,64 2,64 2,64 3,15 2 2,64 2,64 f(amin) 5,91 5,91 5,91 5,7 5,7 1,8 5,91 5,91 αgel (theor.) 12,4 12,4 12,4 12,4 9,9 n.m. 12,4 12,4 Umsatz Epoxy 12,5 14,5 11,2 12,0 10 45* 20 10 KK Verlust nach 2Monaten @23°C 3% 2% 5% 1% n.b. 100% 4% 3% Slipping / mm 0 0 1 0 n.b. 0 nein 4 vernetzt ja ja ja ja ja ja ja nein Verklebungsfestigkeit / MPa 19,7 18,1 19,9 13,4 n.b. n.b. 9,9 AF 20,6 *nach 60d bei 23°C. Aminmenge sollte 20% Epoxidumsatz ergeben. Umsatz steigt kontinuierlich nach 24h waren bereits 20% umgesetzt, nach 500h bereits 30%.
n.b.: nicht bestimmbar, da die Klebmasse bei Raumtemperatur nicht haftklebrig ist
n.m.: Funktionalität der beiden Reaktanden zu gering, um eine Vernetzung erreichen zu können Used raw materials:

Epiclone 673

Solid epoxy-cresol-novolak from DIC with a softening temperature of 75 to 79 ° C. Average functionality: 5.4 epoxy groups / molecule, EEW = 208 - 212 g / eq. Tg = 30 ° C

Epicote 828

Difunctional bisphenol-A / epichlorohydrin liquid epoxide with a weight per epoxide of 184 to 190 g / eq from Hexion. Viscosity at 25 ° C from 10 to 12 Pa s. Average functionality: 2 epoxy groups / molecule. Tg = -16 ° C.

PolyDis PD3611

Nitrile rubber-modified epoxy resin based on bisphenol F diglycidyl ether with an elastomer content of 40% by weight and a weight per epoxy of 550 g / eq from Schill + Seilacher "Struktol". Viscosity at 25 ° C of 10000 Pa s. Average functionality: 2 epoxy groups / molecule. Tg = -10 ° C.

Hypro 1300X45 ATBN

Amine-terminated butadiene acrylonitrile copolymer with 18% acrylonitrile content. Viscosity at 27 ° C of 375 Pa s. Molecular weight 3800 g / mol. Tg = -55 ° C. Functionality = 1.8. The amine used for termination is N-aminoethylpiperazine.

Jeffamine T403

Amine-terminated propylene oxide with 3 primary amino groups that have a methyl group on the neighboring carbon. Tg = -61 ° C. Molecular weight = 440 g / mol, average functionality: 5.7

Jeffamine T3000

Amine-terminated propylene oxide with 3 primary amino groups that have a methyl group on the neighboring carbon. Tg = -70 ° C. Molecular weight = 3000 g / mol, average functionality: 5.91

Dyhard 100S

Latent hardener from AlzChem for epoxy systems consisting of micronized dicyandiamide in which 98% of the particles are smaller than 10 µm.

Dyhard UR500

Latent urone accelerator for epoxy systems in which 98% of the particles are smaller than 10 µm.

Table 1: K = adhesive according to the invention; V = comparative example f Tg / ° C K1 K2 K3 K4 V1 V2 V3 V4 Epiclon N-673 5.4 30th 11.81 11.81 11.81 11.81 20.25 15.81 10.16 PD3611 2 -10 14.73 14.73 14.73 14.73 18th 19.71 12.67 Epikote828 2 -16 11.81 11.81 11.81 11.81 6.75 30th 15.81 10.16 Jeffamin T403 5.7 -61 1.45 1.23 Jeffamin T3000 5.91 -70 9.86 11.44 8.86 21.11 6.8 Hypro 1300X45 ATBN 1.8 -52 60 Dyhard 100S 2.34 2.29 2.38 2.36 2.46 2.87 2.07 Dyhard UR500 0.17 0.16 0.17 0.17 0.19 0.21 0.15 Mixture Tg (epoxy amine mixture) / ° C -18.6 -20.6 -17.2 -4.2 4.3 -25.5 -15.8 f (epoxy) 2.64 2.64 2.64 2.64 3.15 2 2.64 2.64 f (amine) 5.91 5.91 5.91 5.7 5.7 1.8 5.91 5.91 αgel (theor.) 12.4 12.4 12.4 12.4 9.9 nm 12.4 12.4 Sales epoxy 12.5 14.5 11.2 12.0 10 45 * 20th 10 KK loss after 2 months @ 23 ° C 3% 2% 5% 1% nb 100% 4% 3% Slipping / mm 0 0 1 0 nb 0 no 4th networked Yes Yes Yes Yes Yes Yes Yes no Bond strength / MPa 19.7 18.1 19.9 13.4 nb nb 9.9 AF 20.6 * after 60d at 23 ° C. Amine amount should result in 20% epoxy conversion. Conversion rises continuously after 24 hours 20% had already been converted, after 500 hours already 30%.
nb: cannot be determined because the adhesive is not pressure-sensitive at room temperature
nm: The functionality of the two reactants is too low to be able to achieve crosslinking

The epoxy conversion of the adhesives K1-K4 is in the range according to the invention around the theoretical conversion at the gel point. They are cross-linked, pass the slipping test and show comparable bond strengths. Even after storage for 2 months at room temperature, these adhesives retain their pressure-sensitive tack. If the pre-crosslinking is taken too far, as in V3, the adhesives become too cohesive, so that lower values and adhesive failure result in the bonding test. If, on the other hand, there is too little pre-crosslinking, the bond strengths are good, but such adhesives do not pass the slipping test (V4).
If raw materials with too high a Tg are used (V1), the increase in the Tg in the pre-crosslinking step leads to non-pressure-sensitively adhesive systems.

Even if polyamines not according to the invention (without the steric hindrance according to the invention) are used (V2), no pressure-sensitively adhesive systems are obtained, since the epoxides continue to react. Anionic epoxy polymerization occurs and V2 is crosslinked, although such a system with f (epoxy) = 2 and f (amine) = 1.8 cannot theoretically crosslink in a pure addition reaction.

Claims (13)

Process for the production of a pre-crosslinked PSA by bringing the following components into contact and then mixing: a) at least one polyetheramine which contains at least two terminal -NH ₂ groups and in the alpha position to at least one -NH ₂ group contains at least one alkyl radical; b) at least one epoxy resin; c) at least one hardener different from a); d) if applicable, at least one accelerator; and e) optionally at least one additive; whereby _{the epoxy} conversion U epoxy = 0.85 α _gel to 1.3 α _gel and α _{gel is} the gel point of the composition; and
the mixture Tg of components a) and b) is below 0 ° C. Method according to claim 1, characterized in that the mixing i) takes place in a mixer; and or ii) the components being heated together prior to mixing; and or iii) wherein the components are heated during mixing; and or iv) the at least one hardener c) is added at the end of the mixing process at temperatures below 80.degree. Process according to Claim 1 or 2, characterized in that the at least one polyetheramine has a weight-average molecular weight of 150 to 6000 g / mol. The method according to any one of the preceding claims, characterized in that the at least one epoxy resin i) has a Tg of -100 to 60 ° C; and or ii) has an average functionality of 2 to 15; and or iii) has a softening temperature of at least 45 ° C; and or iv) has a viscosity at 25 ° C of at least 10 Pa * s. Method according to one of the preceding claims, characterized in that it contains at least one epoxy resin that is liquid at 23 ° C and at least one epoxy resin that is solid at 23 ° C. Method according to one of the preceding claims, characterized in that the at least one hardener different from a) c) i) is selected from dicyandiamides, phenol novolaks, cresol novolaks, anhydrides, epoxy-amine adducts, hydrazides or mixtures thereof; and or ii) has a T _peak determined by DSC of more than 60 ° C. Method according to one of the preceding claims, characterized in that the at least one accelerator d) is selected from urea derivatives, imidazoles or mixtures thereof. Pre-crosslinked pressure-sensitive adhesive obtainable by a process according to one of Claims 1 to 7. Adhesive tape comprising the pre-crosslinked pressure-sensitive adhesive according to claim 8. Adhesive tape according to Claim 9, characterized in that the pressure-sensitive adhesive has a layer thickness of 20 to 4000 µm. Use of the adhesive tape according to claim 9 or 10 for fixing point holders. Use of the adhesive tape according to claim 9 or 10 for fixing objects in automobiles. A curable composition comprising or consisting of: a) at least one polyetheramine which contains at least two terminal -NH ₂ groups and in the alpha position to at least one -NH ₂ group contains at least one alkyl radical; b) at least one epoxy resin; c) at least one hardener different from a); d) if applicable, at least one accelerator; and e) optionally at least one additive, wherein the mixture Tg of components a) and b) is below 0 ° C.